RATIONALE: Drugs used in chemotherapy work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. Giving more than once drug (combination chemotherapy) may kill more cancer cells. Radiation therapy uses high-energy x-rays to kill cancer cells. It is not yet known whether giving clofarabine or high-dose cytarabine, pegaspargase, and combination chemotherapy followed by daunorubicin hydrochloride or doxorubicin hydrochloride is more effective in treating young patients with acute lymphoblastic leukemia.